1. Field of the Invention
This invention relates generally to the field of vessels that may be used to contain fluids, bulk solids and other materials, and in particular to a bladder used in connection with such vessels.
2. Description of the Related Art
Containment vessels, or tanks as they are sometimes referred to, are used in a wide variety of different industries and industrial, commercial and residential applications to contain fluids (including liquids and/or gases), granular solid material, etc. One particular form of containment vessel or tank that may be used generally comprises a rigid enclosure (often generally round in horizontal section) having an internal bladder that holds the material in question. The rigid enclosure provides structural support, whereas the bladder contains the material for storage in a manner that preserves its purity and integrity, and that limits exposure to the environment. Such vessels or tanks have proven to be advantageous on account of their relatively lightweight and their ease of assembly and disassembly for movement from location to location. Once assembled, the product to be stored is pumped or otherwise conveyed into the bladder. As material is deposited into the bladder the bladder fills the available space provided by the walls of the enclosure. When required, the material within the bladder can be pumped, drained or otherwise conveyed out of the bladder. The types of materials that can be stored in such tanks is extremely broad and can include, amongst other things, water, various gaseous products, liquid or solid food products, grains, industrial metals and minerals, oil, petro-chemicals, etc.
While such bladder tanks or containment vessels have proven to be highly desirable, in some instances it can be difficult to evacuate the entire contents of the bladder, particularly the final amount of material on the bladder floor at the bottom of the vessel, next to its outer walls. In addition, to help reduce capital cost, and to help minimize assembly and disassembly efforts, the top of such bladder containment vessels or tanks is commonly without a rigid lid or cover such that the upper portion of the bladder is exposed to the environment. In some instances, and in particular where the bladder may not be completely filled with material, the exposed upper surface of the bladder may have “low spots” which can lead to puddling or pooling of rainwater or snow and a reduced ability for rain and snow to drain or be directed from the top of the vessel.
Other advantages and features will be apparent from the following description and from the claims.